Method and apparatus for initiating pouring from a blocked opening of a bottom pour vessel

ABSTRACT

An improved refractory closure member having a chamber formed by a removable disc in the normal nozzle opening, into which chamber a reactive gas such as oxygen is introduced to initiate a stream of molten metal from a bottom-pour vessel.

United States Patent 11 1 1111 3,743,139 Lyman Juiy 3, 1973 METHOD AND APPARATUS FOR [56] References Cited INITIATING POURING FROM A BLOCKED UNITED STATES PATENTS OPENING OF A BOTTOM POUR VESSEL 3,581,948 6/1971 Detalie 222 1310. 7 Inventor; Richard E. Lyman Township Zehnder..... Cook County [IL 1,833,739 11/193l Davis 266/42 673,556 5/1901 Hartman 266/42 [73] Assignee: United States Steel Corporation,

Pittsburgh Primary Examiner-Samuel F. Coleman 22 Filed; 9 1971 Assistant Examiner-David A. Scherbel Appi. No.: 169,954

US. Cl 222/1, 222/148, 222/561, 266/34 L, 266/38 Int. Cl B2211 37/00 Field of Search 266/42, 34 L, 38; 222/1, 148, 561, DIG. 7, DIG. 11, D10. 21, DIG. 20

Attorney-Ralph H. Dougherty 5 7 ABSTRACT An improved refractory closure member having a chamber formed by a removable disc in the normal nozzle opening, into which chamber a reactive gas such as oxygen is introduced to initiate a stream of molten metal from a bottom-pour vessel.

8 Claims, 1 Drawing Figure PAIENIEDJUL 3 ms 3.743; 139

INVENTOI? RICHARD E. LrMA/v A/Iomey METHOD AND APPARATUS FOR INITIATING POURING FROM A BLOCKED OPENING OF A BOTTOM POUR VESSEL In the continuous casting of metals such as steel, molten metal is poured from a ladle into an intermediate pouring vessel such as a tundish or a degassing vessel and then into a mold. It is advantageous to control the flow of metal through the bottom-pour opening of the intermediate vessel by means of a sliding gate refractory closure member placed across the opening. The intermediate pouring vessel is usually recessed above the opening. It is usually preferable, and in some cases necessary, to fill the intermediate vessel with the sliding gate in the closed position until the height of the molten metal in the vessel reaches a predetermined level. While the vessel is filling, static molten metal occupies the recess above the opening and solidifies, forming a shell against the sides and across the bottom of the opening.

When the sliding gate is opened, the solidified metal shell is often sufi'iciently thick and strong to prevent the flow of molten metal through the opening. The same condition frequently arises when the sliding gate is closed while pouring is in progress. The usual method of opening a blocked recess has been to burn through the metal shell with an oxygen lance inserted upwardly through the sliding gate nozzle. This is an undesirable practice because it is hard to control the position of the lance and the direction of flow of the oxygen, and usually results in damage to the sliding gate noule and adjacent refractories as well as contamination of the steel. Furthermore, certain casting procedures do not allow sufficient access to the gate nozzle to permit insertion of a lance. Examples are shrouded pouring as shown in my U.S. Pat. No. 3,572,422 and extended tube pouring as shown in Shapland U.S. Pat. No. 3,572,541.

My invention provides means for reliably and controllably initiating a stream of molten metal from a bottom-pour vessel after the vessel has been filled, or after pouring from it has been temporarily discontinued.

Reactive and inert gases are frequently introduced to molten metal to provide various treatments, such as degassing, stirring, decarburizing and equalizing the metal temperature throughout the vessel. It is known to insufflate gas into a mass of molten metal through the vessel lining as shown in Spire U.S. Pat. No. 2,811,346, around the nozzle as shown in Griffiths and Orehoski U.S. Pat. No. 3,253,307, and through the stopper rod as shown in Saccomano U.S. Pat. No. 3,214,804. Further it is known to use sliding gates on bottom-pour vessels, as shown in Shapland U.S. Pat. No. 3,352,465.

Andrzejak, Orehoski, and Shapland, in application Ser. No. 2,224 filed Jan. 12, 1970 and commonly assigned, have disclosed a permeable refractory gate block through which gas is injected into the well of a bottom-pour vessel to agitate the molten metal and suppress the formation of a solid metal shell. When an inert gas, such as argon, is injected in this system, pouring streams do not always begin to flow when the gate is opened. When a reactive gas such as oxygen is injected an objectionable degree of metal contamination may result. Also a metal-oxygen-refractory reaction may erode the working surface of the low density permeable refractory allowing a steel fin to form between the stationary and moving gate refractories when the gate is opened.

it is therefore theprimary object of my invention to provide an improved closure apparatus which includes means for forming a pressure chamber in a sliding gate, and means for introducing gas into the chamber under controlled pressure to initiate molten metal stream flow from a bottom-pour vessel.

It is a further object to provide means for initiating stream flow with no damage to the surrounding equipment.

1t is also an object to provide means for initiating stream flow with no damage to the surrounding equipment.

It is also an object to provide means for initiating stream flow with little or no contamination of the molten metal.

In the drawing:

The single FlGURE is a cross-section through the nozzle of a bottom-pour vessel equipped with a sliding nozzle-lancing gate constructed in accordance with my invention.

The drawing shows a portion of a bottom-pour vessel 10 with a refractory lining 12 for receiving molten metal. The bottom wall of the vessel has a well or recess 13 and an outlet opening 14 lined with erosion-resistant refractory 15. The bottom wall carries a nozzle plate 16 fixed to its underside which has a refractory nozzle 17 aligned with the opening. A sliding gate closure member or noule-lancing gate 18 is mounted beneath the nozzle. Gate 18 has a nozzle opening therein, but can be replaced by a blank gate, not shown. The gate can be supported and operated in any desired manner; hence, I have not shown the supporting and operating mechanism. The gate includes a solid refractory portion 19 having a centrally located refractory nozzle 20 and is covered on its sides and bottom by a steel jacket 21. A heavy-walled pipe 22 extends through jacket 21 and nozzle 20 where it is afiixed in a slag-resistant basic refractory 23.

Nozzle 20 carries in its bore a cup or disc 25 which has a small orifice 26, preferably off center of the disc. The inside diameter of pipe 22 should be larger than the diameter of orifice 26. The disc is made of a lightweight material, such as aluminum or plastic, having a melting point of or below that of molten steel. in some cases, a suitable thickness steel disc may be employed.

Oxygen or other reactive gas is supplied to pipe 22 through an oxygen supply line 28 which carries a cupshaped end fitting 29.

When vessel 10 is prepared to receive molten metal, a blank gate is placed into the position of gate 18. The molten metal that settles into outlet 14 develops a solidified skin 30 as it loses heat to its surroundings. When it is desired to begin teeming metal from vessel 10, gate 18 is moved into position beneath nozzle 17. 1fv the ferrostatic head in the vessel is not sufficient to break the solidified metal skin, the oxygen supply line 28 is moved into position so that fitting 29 encloses the exterior opening of pipe 22 and the flow of oxygen through supply line 28 is begun. The oxygen moves through pipe 22 and circulates turbulently within the pressure chamber defined by the bore of nozzle 20 and disc 25, discharging through orifice 26 in disc 25 as well as through any leaks that might exist between the bottom of nozzle plate 16 and the top of sliding gate 18. I prefer to introduce the reactive gas at a pressure lower than the fluid head of metal. Oxygen will react with hot steel, burning in the chamber and melting the solidified shell. Thus, if the shell 30 is thin and sufficiently hot to be perforated only by the action of buming and melting, no gas will pass upwardly through outlet 14 into the metal.

If no stream appears within a short time, I increase the gas flow and concomitantly the gas pressure in the chamber to a value substantially greater than the ferrostatic pressure on the shell to provide a rupturing force to the bottom of shell 30 in addition to the thermochemical effect from the oxidation of the iron. in the latter case, gas bubbles may pass upwardly into the molten metal as the solidified shell 30 is ruptured. Since only a minimal volume of gas is present within the chamber, the resultant degree of metal contamination is insignificant. Upon perforation of shell 30, molten metal moves downwardly against cup 25 instantly melting it and thus clearing the passageway through nozzle 20. As stream flow begins, the gas pressure in the chamber is instantaneously discharged and flow of gas through pipe 22 is immediately shut oiT, which may be accomplished by merely removing end fitting 29 from the end of heavy-wall pipe 22. Molten metal will enter pipe 22 and the effect of the heavy wall will be to chill the molten metal and cause it to freeze therein, effectively sealing the pipe against leakage.

If a stream appears, but stream flow ceases in a short time because of an excessively chilled condition in vessel 10, I replace noz'zle-lancing gate 18 with a second nozzle-lancing gate 32 having a disc 33 with greater resistance to perforation than the disc in the first gate. This allows a more sustained lancing action in the nozzle. This procedure may be repeated with a gate having a still more resistant disc if required until stream flow is continuous.

Although my invention has been shown and described with respect to a bottom-pour vessel, it is apparent that it is applicable to any nozzle-type pouring vessel, regardless of whether the nozzle is in the bottom wall, side wall, or corner of the pouring vessel.

It can readily be seen from the foregoing that l have invented a method and apparatus for initiating a pouring stream from a blocked teeming nozzle of a pouring vessel that causes no damage to the surrounding equipment, and little or no contamination to the molten metal. The method is positive because oxygen injectipn at the necessary pressure can be continued until a stream is obtained.

I claim:

1. A gate for opening a teeming nozzle of a molten-metal-containing nozzle-pouring vessel, said nozzle being subject to blocking by solidified metal, said gate comprising:

a refractory body having an opening therethrough;

a disc made of a material having a melting point below that of the molten metal in the vessel, said disc being seated in said opening for restricting the flow of a gas through said opening, said disc and said body defining a chamber; and

means connected to said body and communicating with said chamber for introducing gas to said chamber.

2. A gate as defined in claim 1 in which said disc has a small orifice therein.

3. A gate as defined in claim 2 in which said means comprises a heavy-walled metal pipe fixed in said body.

4. A gate as defined in claim 3 in which the diameter of the orifice in said disc is less than the internal diameter of said pipe.

5. A gate as defined in claim 1 in which said means comprises a pipe fixed in said body.

6. A method of initiating pouring from a nozzle-pour vessel containing molten metal, the pouring opening of which vessel has become blocked by solidification of a skin of metal in the region of the opening, said method comprising:

providing a sliding gate refractory closure member beneath said pouring opening, said gate having an opening being at least partially blocked by a perforable device for restricting gas-flow therethrough, said gate including means for introducing gas to the chamber defined by said gate opening, said device and said skin of metal;

introducing a reactive gas to said chamber at low pressure, whereby said gas will burn and melt said skin;

maintaining gas flow until said solidified skin of metal is perforated by the action of burning and melting, simultaneously initiating metal flow;

said metal then melting said device and thereby passing through said gate opening, and

sealing said gas-introducing means.

7. A method of initiating pouring from a nozzle-pour vessel containing molten metal, the pouring opening of which vessel has been opened by the method as defined in claim 6 and has subsequently become blocked anew by excessively chilled steel from the vessel being teemed therethrough, said method comprising:

replacing said sliding gate refractory closure member beneath said pouring opening by a second gate having a gate opening at least partially blocked by a second device for restricting gas-flow therethrough, said second device being more resistant to perforation than said first named device in said first gate, said second gate including means for introducing gas to the chamber defined by said second gate and said second device;

introducing a reactive gas to said chamber at low pressure, whereby said gas will burn and melt said skin;

maintaining gas flow until said solidified skin of metal is perforated by the action of burning and melting, simultaneously initiating metal flow;

removing said second device;

sealing said gas-introducing means, and

repeating the above steps each time with a more resistant device than in the previous step until a continuous stream flow is obtained.

8. A method of initiating pouring from a nozzle-pour vessel containing molten metal, the nozzle-pour opening of which vessel has become blocked by solidification of a skin of metal in the region of the opening, said method comprising:

positioning a sliding gate refractory closure member beneath said nozzle-pour opening, said gate having a gate opening which is aligned with said first named opening and is at least partially blocked by a device for restricting gas-flow therethrough, said skin and said device defining a chamber within said gate opening, said gate including means for introducing gas to said chamber;

introducing a reactive gas to said chamber at low pressure;

incrementally increasing the gas pressure by increasing gas flow until the action of burning, melting and pressure on said solidified skin of metal causes said skin to rupture, simultaneously initiating metal flow;

removing said device while maintaining said gate 

1. A gate for opening a teeming nozzle of a molten-metalcontaining nozzle-pouring vessel, said nozzle being subject to blocking by solidified metal, said gate comprising: a refractory body having an opening therethrough; a disc made of a material having a melting point below that of the molten metal in the vessel, said disc being seated in said opening for restricting the flow of a gas through said opening, said disc and said body defining a chamber; and means connected to said body and communicating with said chamber for introducing gas to said chamber.
 2. A gate as defined in claim 1 in which said disc has a small orifice therein.
 3. A gate as defined in claim 2 in which said means comprises a heavy-walled metal pipe fixed in said body.
 4. A gate as defined in claim 3 in which the diameter of the orifice in said disc is less than the internal diameter of said pipe.
 5. A gate as defined in claim 1 in which said means comprises a pipe fixed in said body.
 6. A method of initiating pouring from a nozzle-pour vessel containing molten metal, the pouring opening of which vessel has become blocked by solidification of a skin of metal in the region of the opening, said method comprising: providing a sliding gate refractory closure member beneath said pouring opening, said gate having an opening being at least partially blocked by a perforable device for restricting gas-flow therethrough, said gate including means for introducing gas to the chamber defined by said gate opening, said device and said skin of metal; introducing a reactive gas to said chamber at low pressure, whereby said gas will burn and melt said skin; maintaining gas flow until said solidified skin of metal is perforated by the action of burning and melting, simultaneously initiating metal flow; said metal then melting Said device and thereby passing through said gate opening, and sealing said gas-introducing means.
 7. A method of initiating pouring from a nozzle-pour vessel containing molten metal, the pouring opening of which vessel has been opened by the method as defined in claim 6 and has subsequently become blocked anew by excessively chilled steel from the vessel being teemed therethrough, said method comprising: replacing said sliding gate refractory closure member beneath said pouring opening by a second gate having a gate opening at least partially blocked by a second device for restricting gas-flow therethrough, said second device being more resistant to perforation than said first named device in said first gate, said second gate including means for introducing gas to the chamber defined by said second gate and said second device; introducing a reactive gas to said chamber at low pressure, whereby said gas will burn and melt said skin; maintaining gas flow until said solidified skin of metal is perforated by the action of burning and melting, simultaneously initiating metal flow; removing said second device; sealing said gas-introducing means, and repeating the above steps each time with a more resistant device than in the previous step until a continuous stream flow is obtained.
 8. A method of initiating pouring from a nozzle-pour vessel containing molten metal, the nozzle-pour opening of which vessel has become blocked by solidification of a skin of metal in the region of the opening, said method comprising: positioning a sliding gate refractory closure member beneath said nozzle-pour opening, said gate having a gate opening which is aligned with said first named opening and is at least partially blocked by a device for restricting gas-flow therethrough, said skin and said device defining a chamber within said gate opening, said gate including means for introducing gas to said chamber; introducing a reactive gas to said chamber at low pressure; incrementally increasing the gas pressure by increasing gas flow until the action of burning, melting and pressure on said solidified skin of metal causes said skin to rupture, simultaneously initiating metal flow; removing said device while maintaining said gate opening in alignment with said nozzle-pour opening; and sealing said gas-introducing means while maintaining metal flow through said gate by molten metal entering said means and solidifying therein. 